1. Field of the Invention
The present invention relates to a method of manufacturing a fiber-reinforced shaped article of plastics material for pipeline systems. The article includes an inner casing of a thermoplastic material and an outer casing of a fiber winding impregnated with synthetic resins.
2. Description of the Prior Art
In pipeline systems for conducting media, particularly aggressive media in the chemical industry, pipelines are used which have an inner casing of a thermoplastic material, such as, polyethylene, polypropylene, polyvinyl chloride, etc., and an outer casing of a fiber-reinforced laminate, such as, wound glass fiber impregnated with an unsaturated polyester resin or epoxy resin. The outer casing of laminate has the purpose to reinforce the pipes, so that media can be conducted at increased pressures and external forces can be absorbed, such as, tensile or compressive bending forces acting on the pipeline.
Pipeline systems of this type require appropriately shaped pieces, for example, T-pieces, crosspieces, angles, bends or reducing sleeves, as they are necessary in the conventional pipeline construction.
In the known methods for manufacturing such shaped articles or pieces, the winding is carried out in a so-called wet procedure, i.e., the glass fibers or the glass fiber tapes are impregnated with resin during the winding procedure. However, when winding is carried out with machines operating according to the lathe principle, only simply shaped pipe pieces or bend pieces can be wound using the wet procedure. Such a winding procedure using a machine cannot be used for complicated pieces, such as T-pieces or crosspieces, because the tape including the container with the impregnating substance, would have to be rotated above its longitudinal axis during the windings. In addition, the glass fiber fabric tapes cannot be sufficiently impregnated with resin when high winding speeds are employed.
It is, therefore, the primary object of the present invention to provide a method of the above-described type in which even complicated glass fiber-reinforced articles can be manufactured by means of a machine and in which a uniform quality and the necessary strength of the articles is ensured. It should be possible to use the method for all types of pieces used in pipeline construction and it should be possible to manufacture the pieces automatically in large numbers while keeping the costs low.